I've had a Nature's Head for three seasons now. I would not go back to a regular marine toilet.
I had a fruit fly "mishap" last year - solved by putting a bit of screen over my head's vent and using coconut coir instead of peat moss. (You can buy this at Petco or similar large pet store that has reptile bedding: Zilla Coconut Husk Brick Reptile Bedding at PETCO
Absolutely no smell.